Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=true, so the safety profile is known. The description adds real value beyond them: it discloses merge semantics (only supplied fields change, the rest is preserved) and confirms no message is sent to the contact — a side-effect guarantee an agent cannot infer from the schema. It does not explain why destructiveHint is true (e.g. that notes/tags are overwritten) or any permission requirements.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, front-loaded with the action and resource, then the merge rule, then the side-effect disclaimer. No filler or repetition; only slight loss is the telegraphic field list without grouping or limits.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 6-parameter mutation tool with no output schema and low schema coverage, the definition covers intent, partial-update behaviour and the no-message guarantee. It leaves out what is returned on success, how an invalid conversation_ref is handled, and the overwrite implications behind destructiveHint=true, which an agent calling this needs to know before replacing notes or tags.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is only 17% (just conversation_ref), so the description has to compensate and partly does by naming all five updatable fields in Spanish, mapping them to stage, priority, profile_type, tags and notes. It adds no enum semantics, no length/count limits (tags max 20, notes max 5000) and no explanation of what AUTO/PERSONAL/BUSINESS imply, so half the burden stays on the bare schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('Guarda') plus the resource ('ficha del cliente de un chat de WhatsApp') and enumerates the fields it covers (etapa, prioridad, tipo, etiquetas, notas). The final line 'No manda nada al contacto' implicitly separates it from the messaging siblings (whatsapp_send_message, send_message), though no sibling is named explicitly.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The partial-update rule ('Cambia solo lo que pases; el resto de la ficha queda igual') tells the agent how to call it, and 'No manda nada al contacto' rules out a messaging intent. There is no explicit statement of when to prefer this over whatsapp_add_contacts or set_conversation_bot, and no prerequisites or error conditions are given.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.